It is well known that overall fuel efficiency in a multiple-cylinder internal combustion engine can be increased by selective deactivation of one or more of the engine valves under certain engine load conditions. A known approach to providing selective deactivation is to equip the hydraulic lifters for those valves with means whereby the lifters may be rendered incapable of transferring the cyclic motion of engine cams into reciprocal motion of the associated pushrods. Typically, a deactivation lifter includes, in addition to the conventional hydraulic lash elimination means, concentric inner and outer portions which are mechanically responsive to the pushrod and to the cam lobe, respectively, and which may be selectively latched and unlatched to each other, typically by the selective engagement of pressurized engine oil.
U.S. Pat. No. U.S. Pat. No. 6,164,255, issued Dec. 26, 2000 to Maas et al., discloses a deactivation hydraulic valve lifter comprising an outer section which encloses an inner section that is axially movable, the outer section having a pot-shaped configuration and a bottom which comprises an end for cam contact and separates the inner section from a cam whereby, upon coupling of the sections by a coupling means, a high lift of a gas exchange valve is effected, and upon uncoupling of the sections, a zero lift. The disclosed coupling means is a single round pin disposed in a transverse bore in the inner section and biased outwards by a coil spring to engage a mating round bore in the outer section, whereby the two sections may be locked together. The bore in the outer section is matable with an oil gallery in the engine block, whereby pressurized oil may be introduced against the head of the locking pin to urge the pin hydraulically into retraction within the inner section to uncouple the inner and outer sections and thereby deactivate the associated engine valve.
U.S. Pat. No. 6,196,175 B1, issued Mar. 6, 2001 to Church et al. discloses a mechanism similar to that disclosed by Maas et al. A single locking pin is selectively extendable from the pin housing into a round locking bore in the lifter body. In addition, an alignment member extends from the pin housing opposite the locking bore through a slot in the lifter body and engages an axially extending slot in the engine block to prevent rotation of the pin housing relative to the lifter body, thus maintaining alignment of the locking pin with the locking bore.
U.S. Pat. No. 6,513,470 B1, issued Feb. 4, 2003 to Hendriksma et al., discloses an improved mechanism useful in a valve deactivating hydraulic lifter. The mechanism includes a pair of opposed locking pins disposed in a transverse bore in the inner section to engage the outer section in two separate locations 180° apart. Further, the outer section single round bore of Maas et al. and Church et al. is replaced by an annular groove formed in the inner wall of the outer section and defining an annular locking surface such that all rotational alignment requirements are removed, the pins being engageable into the groove at all rotational positions of the inner section within the outer section. The groove communicates, similarly to the round bore in Haas et al., with an oil gallery in the engine block for actuation and deactuation of the locking pins. Since the lifter in Hendriksma, et al. uses two locking pins instead of one, as disclosed in Maas, et al. and Church et al, the force applied through the lifter to open the valve is centralized advantageously along the centerline of the lifter thereby improving the smoothness of operation of the locking feature. Further, the pins are flattened in the portion which engages the locking surface to distribute the load over a broad area of the locking surface.
Hendriksma et al. discloses that complete rotational freedom of the pin housing within the lifter body is an advantage in that wear is distributed over time along the entire length of the annular locking surface. However, such total freedom can also be disadvantageous. When the lifter is used in an application such as a V-style or slant engine where the lifter body can be tipped as much as 45° from vertical, the rotational orientation of the pin housing within the lifter body at the time of engine shutdown can be very important. If the oil supply port through the pin housing and the oil supply port in the plunger element are both on the underside of the pin housing when it comes to rest, oil within the plunger element can leak therefrom via tolerances between the pin housing and the lifter body. Then, when the engine is restarted, air is drawn into the high pressure chamber of the lash adjuster causing noisy engine operation for a period of time after the engine is restarted, before the plunger element can be refilled by engine oil. Such noisy operation is obviously highly undesirable and can lead to premature wear of engine components.
It is a principal object of the present invention to provide a deactivation lifter having means for preventing draining of oil from the lifter during periods of engine shutdown.